**ON A/C 051-099, 201-219,
A. Receive Function The HF audio integrating signals transmitted by the stations are picked-up by the antenna and transmitted to the antenna coupler. The coupler adapts the impedance between the antenna and HF transceiver. The signal from the HF coupler is transmitted to the HF transceiver by a coaxial cable. The HF transceiver, tuned on the selected frequency by one of the RMP, demodulates HF signals into AF signals. The AF signals are transmitted via the AMU, to the audio equipment or SELCAL system.
B. Transmit Function The AF signals from the microphones are transmitted to the HF transceiver through the AMU. The HF transceiver tuned on the frequency selected by one of the RMP, transforms the AF signals into HF modulated signals. The HF signals are fed to the antenna by the coaxial cable and antenna coupler. They are then transmitted to the various stations. A connection between the HF transceiver and the SDAC enables to record the use of the HF system in transmit mode. The connection is obtained through the PTT switch.
R **ON A/C 106-149, 220-299, 301-399, 401-499,
A. Receive Function The HF audio integrating signals transmitted by the stations are picked-up by the antenna and transmitted to the antenna coupler. The coupler adapts the impedance between the antenna and HF transceiver. The signal from the HF coupler is transmitted to the HF transceiver by a coaxial cable. The HF transceiver, tuned on the selected frequency by one of the RMP, demodulates HF signals into AF signals. The AF signals are transmitted via the AMU, to the audio equipment or SELCAL system.
B. Transmit Function The AF signals from the microphones are transmitted to the HF transceiver through the AMU. The HF transceiver tuned on the frequency selected by one of the RMP, transforms the AF signals into HF modulated signals. The HF signals are fed to the antenna by the coaxial cable and antenna coupler.
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They are then transmitted to the various stations.
A connection between the HF transceiver and the SDAC enables to record
the use of the HF system in transmit mode.
The connection is obtained through the PTT switch.
On ground, the GND HF DATA LINK pushbutton switch is used to override the
data transmission inhibition of the HF1 transceiver.
**ON A/C ALL
C. Indication of Transmission Out of Frequency Range The HF system is designed to operate within the frequency range from 2.8 to 23.999 MHz. However, the RMP enables frequency display in the 2 to 29.999 MHz range. If the out-of-range values of the HF transceiver are displayed on the RMP, the operating anomaly is indicated as follows:
-at first activation of the PTT switch: a 1000 Hz audio signal is triggered
-interruption of the signal after 15 s approximately
-triggering of the signal at each attempt to transmit.
8. Test
____
**ON A/C 001-049, 101-105, 151-199,
A. Built-In Test Equipment (BITE) The BITE facilitates maintenance on in-service aircraft. The BITE detects and determines a failure related to the HF system. The BITE of the HF transceiver is connected to the Centralized Fault Display Interface Unit (CFDIU) (Ref. ATA 31-32). The BITE:
-transmits permanently HF system status and its identification message to the CFDIU
-memorizes the failures occurred during the last 63 flight segments
-monitors data input from the various peripherals (RMP and CFDIU)
-transmits to the CFDIU the result of the tests performed and self-tests
-can communicate with the CFDIU by the menus.
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B. General Operation
The BITE may operate in two modes:
-
the normal mode
-
the menu mode.
(1)
The normal mode During the normal mode, the BITE monitors cyclically the status of the HF system. It transmits its information to the CFDIU during the flight concerned. In case of fault detection, the BITE stores the information in the fault memories. These items of information are transmitted to the CFDIU every 100 ms by an ARINC 429 message with label 356.
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